LExEn: Genetic and Physiological Analysis of the Determinants of Halophillism in Halomonas Elongata

人们普遍认为地球上的生命起源于海水。虽然原始细胞出现在环境中，其中Na +是最丰富的阳离子，生物体已经进化到维持细胞质浓度的Na +远低于外部Na +浓度。Na +在细胞质膜上的不均匀分布所产生的势能用于驱动各种过程，如营养摄取、细胞运动和神经元的电活动。高浓度的NaCl对大多数生物体都是有毒的，因此，高盐度是极端环境的一个例子。 有有限数量的微生物需要高浓度的NaCl，这将抑制大多数其他微生物。依赖于高浓度NaCl的物种被称为嗜盐菌。 虽然人们普遍认为嗜盐菌需要高浓度的Na +来驱动营养吸收，但这尚未得到最终证明。最嗜盐的真细菌之一是长盐单胞菌，其需要至少0.5 M NaCl。该研究项目正在验证H。长穗醋栗需要高浓度的Na +，因为它的一些能量依赖性反应，如营养物质的运输或ATP的合成，是由Na +梯度驱动的。这种微生物特别适合于分析嗜盐性的决定因素，因为它可以在简单的限定盐培养基中生长，并且作为变形菌门（包括E.大肠杆菌），它适合于遗传分析。 本研究的具体目的如下：1）确定长盐单胞菌（Halomonaselongata）甜菜碱转运系统的Na+需要量。 选择该转运蛋白进行分析是因为它已经在E.大肠杆菌中的Na ~+，使其在非嗜盐背景下的活性是否具有与大肠杆菌相似的Na ~+需求成为可能。coli中的嗜盐背景。长形的 2)确定葡萄糖和氨基酸的转运系统在H.长形的3)克隆H. elongata的Na +需要量进行了比较研究。elongata和E.杆菌 这些研究具有一定的实际意义，有助于H. elongata和其他嗜盐菌，用于高盐地区环境污染物的解毒。

It is generally accepted that life on Earth originated in sea water. Although primordial cells arose in an environment in which Na + is the most abundant cation, organisms have evolved to maintain the cytoplasmic concentration of Na + much lower than the external Na + concentration. The potential energy generated by unequal distribution of Na + across the cytoplasmic membrane is used to drive diverse processes, such as nutrient uptake, cell motility, and the electrical activity of neurons. NaCl at high concentrations is toxic to most organisms, and therefore, high salinity is one example of an extreme environment. There are a limited number of organisms which require high concentrations of NaCl that would be inhibitory to most other organisms. Species which are dependent on high concentrations of NaCl are called halophiles. Although it is generally believed that halophiles require elevated concentrations of Na + to drive nutrient uptake, this has not been proven conclusively. One of the most halophilic eubacteria is Halomonas elongata, which requires at least 0.5 M NaCl. The research project is testing the hypotheses that H. elongata requires high concentrations of Na + because some of its energy-dependent reactions, such as transport of nutrients or the synthesis of ATP, are driven by a Na + gradient. This organism is uniquely suitable for the analysis of the determinants of halophilism because it can grow in a simple defined salts medium and, as a member of the g-division of the Proteobacteria (which includes E. coli), it is amenable to genetic analysis. This research has the following specific aims: 1) Determine the Na+ requirement of the transport system for glycine betaine in Halomonas elongata. This transporter is chosen for analysis because it has already been expressed in functional form in E. coli, making it possible to test whether its activity has similar requirements for Na + in the non-halophilic background of E. coli as in the halophilic background of H. elongata. 2) Determine whether the transport systems for glucose and amino acids have high Na + requirement in H. elongata. 3) Clone the gene for the glucose transporter of H. elongata and carry out comparative studies of the Na + requirement of the product of this gene in H. elongata and in E. coli. These studies have the practical benefit that they will contribute to the development of H. elongata and other halophiles for the use of detoxification of environmental pollutants in highly saline areas.